


Not With A Whimper But A Bang

by NaoNazo



Category: Avatar: The Last Airbender, Fullmetal Alchemist - All Media Types
Genre: Crack, Koh the facestealer taking the place of Truth in this AU, don't ask me when in the series this happens, now with additional 'Elrics meet Zuko/Li in Ba Sing Se' chapter, title and chapter titles come from T.S. Eliot's The Hollow Men bc I am a Nerd
Language: English
Status: In-Progress
Published: 2019-11-06
Updated: 2020-01-23
Packaged: 2021-01-23 23:41:40
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 4,395
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21328612
Author URL: https://archiveofourown.org/users/NaoNazo/pseuds/NaoNazo
Summary: The irony here, of course, is Zuko identifying SOMEONE ELSE as ‘the grumpy one.’
Comments: 151
Kudos: 1631
Collections: Clever Crossovers & Fantastic Fusions





	1. With Direct Eyes

**Author's Note:**

  * Inspired by [snipers solve 99% of all problems](https://archiveofourown.org/works/20644262) by [silentwalrus](https://archiveofourown.org/users/silentwalrus/pseuds/silentwalrus). 

Toph is the first one to notice something different.

Or at least, that's what Katara assumes is happening when the little gremlin up and runs away while they're entering the mining village. Muttering under her breath that not all of them can have _eyes _on their _feet_ and that they're supposed to give at least a bit of warning before pulling a vanishing act (not that anyone but Aang ever listens to her, Katara despairs over the chain of command in their little group), Katara follows.

The boy Toph accosts with an accusing shout of "YOU!" looks entirely unremarkable. He's wearing the typical earth-brown and yellow robes most of the other villagers are wearing, although his hands are gloved and his cap covers his hair completely.

Still, Katara reaches out to pull Toph back when she sees his eyes, narrowed suspiciously at them. Gold eyes.

Fire Nation gold.

Toph shakes off her hand. "YOU!" she shouts again, stomping a foot. "HOW ARE YOU DOING THAT?"

The boy looks bored, of all things. "Doing what?"

"You're bending metal!" Toph cries, gleeful in the way she normally is when they reach a large patch of mud. "Teach me!"

The boy looks significantly less bored and a lot more alert of their surroundings. "Shut up!" he hisses, darting a look around the square. Not like there are that many other people walking by, but Katara is mainly focused on the part where Toph thinks this pipsqueak stranger is doing the impossible. And Katara isn't blind, but the boy's just standing there? He isn't doing anything remarkable, unless you count his menacing scowl.

Besides, everyone knows it's impossible to bend metal.

"You GOTTA teach me," Toph presses, getting close to begging in a way Katara's never seen before. "Come on, we're fighting the Fire Nation all the time, it would be SO COOL if I could just bend their armor shut!"

The boy folds his arms and stares at Toph, almost like he's trying to hold a staring competition. Katara wishes him luck. Toph always wins against Sokka.

"You're gonna fight the Fire Nation?" he asks. "Just you?"

Toph grins. "Well, you know. You could always come with."

Katara objects. "Toph, we don't know anything about him! We can't just--"

"Come on, I'm helping the Avatar learn earthbending," Toph interrupts, barrelling over Katara's objections. "Mainly that's just tossing rocks at him until he remembers not to run away, for now."

The boy snorts with laughter. "Yeah, that's what my teacher did, too. Look, I got something to do but... after that, maybe." He raises a hand to shoo them away. "Find me in a couple days. When all the explosions die down."

"The_ wha_\--"

"Sure thing, Metal-Man!" Toph chirps, digging a pointy elbow into Katara's ribs.

"Call me Ed, shorty," the boy tosses a smirk over his shoulder and leaves.

\----------

Very shortly, they find out that Ed was not in the least bit kidding about the explosions, even if they mainly occurred on a shipyard containing imprisoned earthbenders from the surrounding villages. They see neither hide nor hair of Ed until three days after the Fire Nation soldiers were found imprisoned on their own ship, trapped by enormous metal hands that had apparently surged from the floor. Toph cackled for half an hour straight before Aang could convince her to transfer the soldiers into a more... usual set of confinements.

Katara almost doesn't recognize Ed when he returns, limping slightly as he supports a boy with the same Fire Nation gold eyes on his shoulder. Partly it's the expression on his face, soft and fond as he regards the kid who could only be his little brother. Partly it's the fact that he apparently lost his hat somewhere and exchanged his sensible Earth Kingdom robe for a brilliantly red one that must have been taken from the prison ship. 

She's never seen a person with gold hair before, let alone two. The red robe against his tanned skin and the sunlight against his gold hair-- well. She can't be blamed if she blushes a bit when she introduces Ed and his brother to Aang and _her_ brother.

It takes less than a day for her to revise her opinion on the brothers. Not Al, Al is a darling and apparently just as much of a genius earthbender as Toph and his brother. He's calm, quiet, sturdy as groundrock, just the way she'd always thought an earthbender would be.

Ed, it turns out, is a bottomless pit with table manners to rival Toph, a hot temper to rival _Prince Zuko_ if you mention his height and, unfortunately, enough talent at earthbending that she can't reasonably suggest they leave him somewhere quiet and remote for the rest of the war.

The first time they encounter Fire Nation soldiers, he and Toph make a game out of flinging mud pies at them before fast-baking the mud into clay to keep them from moving. 

The second, Ed and Al dress up like lost kids from the colonies and stay with the band of soldiers long enough to identify and steal their entire food supply, which barely fits in Appa's saddlebags. Oh, and five suits of their armor to reshape into weapons, Ed explains, with a terrible glint in his eye.

By the third, Toph and Al work together to attack with flying chains while Ed somehow transforms something under his sleeve into a knife, and by now Katara just stands back with her head in her hands and waits for it to be over so she can practice her healing. On the fire nation soldiers, because while Aang may have serious talks with them about the importance of restraint and doing no more harm than necessary, Ed and Al fight like rabid polar-bear-dogs, and she's starting to feel sorry for the poor fools who stumble across their party.

She still knows next to nothing about the brothers-- despite reminding them multiple times that she's here if they ever want to talk, about _anything_\-- but at this point, she's starting to think that not even the Fire Lord could seriously challenge them in a fight.

Dear Oma and Shu, what is that burning smell, are they playing with lava again, whose idea was it to give these terrible tiny monsters the power to play with flaming molten rock, and why is she the only person who thinks they should not be flinging it around like a fun toy, she would like to submit a _complaint_ to the Spirit World for making her deal with this.


	2. Violent Souls

The kids who walked into Pao's teashop were doing possibly the worst job Zuko had ever seen of pretending not to be Fire Nation. Sure, they had hats on, poorly-knitted lumps of fabric like the hat Lieutenant Jee sometimes wore under his helmet when they sailed too far South.

Uncle had tried to make him wear one, to keep his head warm, he said. Back when Zuko had his phoenix tail and shaved the rest (yes, he knew it looked weird, but not as weird as the great ugly scar on his face, so. Anyway, the healers had shaved it that way first and it just got to be a habit.). Still. He was a _firebender_. He could keep his own head warm.

Anyway. The kids. Walking in with eyes darting to exits and possible weapons, steps light and sure, hands hooked in pockets like they'd be able to fly up in a moment if they needed to bend.

Eyes bright gold like Agni's chosen children.

Zuko didn't even need to walk near them to know the air would be slightly warmer, like sitting next to Uncle Iroh while he drank tea on the stern. He wasn't sure if other benders had that same innate sense for their element-- not like he was ever going to have the chance to _ask_\-- but he'd always been able to find the flow of heat in a room.

It came in handy when he was trying to hide from Azula.

Anyway, the two definitely-Fire-Nation kids walked into the tea shop and sat down at a table in his section. The one who wasn't wearing gloves looked around with a delighted smile that reminded Zuko eerily of his Uncle about to proverb.

The shorter one looked up to meet his eyes and scowled.

Zuko scowled back reflexively. 

By any objective standard, his scowl was _better_. For one thing, the scar that had very nearly permanently sealed his eyelid shut made it look like he was always pissed. Which he _wasn't_, except when there was something to be pissed _about._

For another, the kid's round face and baby cheeks made him look about ten. Zuko had been practicing this scowl in the mirror _long_ before the kid learned to talk. He had scowl seniority.

"Hello!" The cheery one chirped. "We heard this place had the best tea in Ba Sing Se."

The grumpy one's scowl morphed into a softer, fonder frown. Zuko sighed.

"We do. What kind of tea do you want?" He pointedly refrained from calling it hot leaf juice. Uncle said they didn't need that much truth in advertising.

"Hmmm..." the cheery one glanced around as he thought. "What would you recommend?"

That they leave the shop before someone reported a meeting of people with obviously Fire Nation features and got him and Uncle involved in another mess.

"... the jasmine?" he hazarded.

The grumpy one snorted. He scowled again.

"Heard you might have some lotus tea," the grumpy one said. Pointedly. Zuko blinked at him.

"...no?" He responded. Lotus tea was what Uncle usually asked for when they hit a large enough port, and they always went in the back to check and never found any. Plus, it sounded gross.

Not as gross as some of the teas Uncle had made him drink over the years, but still. Ew.

The grumpy one frowned. "You're _sure_ you don't have any lotus tea?" he asked suspiciously.

Zuko crossed his arms. "I help check the stock every night. We've never had lotus tea." Maybe it was a Colonies thing, the tea. He'd never been forced to deal with it when he was. Well.

"Can you check in the back?" the cheery one asked, in a way that strongly implied he was trying to say something else. Uncle also used that tone a lot, and Zuko almost never managed to figure out what the 'something else' was.

He threw up his arms. "Fine! I'll go check in the back _where I work_ to find lotus tea _we definitely don't have_." 

"Thank you!" said the cheery one. The grumpy one rested his chin on his gloved palm and rolled his eyes.

Zuko stomped back to the kitchen to <strike>complain to Uncle </strike> check their stock for lotus tea they absolutely never bought.

Uncle was oddly sympathetic, coming out of the kitchen to personally apologize to the brothers-- with that much facial similarity, they could almost be twins. Maybe if they were born at the same time, one of them got all the people skills and the other one got all the scowling muscles-- and make them a different pot of tea.

He also invited them to a game of pai sho that night, which Zuko was sure as hellfire going to avoid. Let someone else deal with the proverbs and the 'no that tile doesn't move that way' disappointed stare and the bucketfuls of tea. 

Besides, Zuko had... a date. Apparently.

This... was not going to go well.

**Notes for the Chapter:**

> The irony here, of course, is Zuko identifying SOMEONE ELSE as ‘the grumpy one.’


	3. Those Who Have Crossed

Roy Mustang meets the brothers a day after they are spat bleeding and blank-eyed out of the spirit world. He has often, often considered the cruelty of the universe that the spirits could not have held them for one more day.

Roy, firebender, administrator of the Fire Nation military outpost of Qingdao ( a colony in the former Earth Kingdom next to Yu Dao and much less famous), one of the heroes of the battle of Ba Sing Se, was in town on a conscription call.

What this generally means is that he takes his team to the outlying villages of Qingdao, grabs a few young men of the right age who stand still long enough to be “conscripted,” and then manages to lose at least half of them on the journey back to the outpost. 

What this specifically means is that Havoc, Breda and occasionally Fuery will travel ahead of his party to secure them a hotel, and spend the night drinking in any bar that’s open and loudly proclaiming how much of an honor it is that all the young men of this town will be joining the war effort the next day. And how unfortunate that the last town they passed through had caught an epidemic that killed or crippled a good portion of their youth, but surely it hasn’t spread this far North yet?

Falman likes to come along and demonstrate his famous “how to untie Fire Nation knots while tied up” act to groups of kids he sees on the street. His act is very popular.

Many of the towns in the outskirts of Qingdao have what appear to be yearly epidemics.

And all of their children are uncannily good at knots.

Still, there are some orders Roy is much less able to skirt around, and order number one is “investigate any reports of bending and apprehend those responsible.” 

Roy is never completely sure how the smoking, kilometer-long crater in front of the Elrics’ fire-ravaged house came to be, but it’s sure as hell an obvious sign of _ some _ kind of bending.

Riza Hawkeye, Roy’s Yuyan archer second-in-command, almost audibly rolls her eyes when she sees the smoke. “Sir,” she says. 

He allows her to precede him as they trace the smoke back to its source. She nocks an arrow to her bow, ready to draw and fire at will.

She lowers the bow when they reach the crater. Some of the grass is still smoking, but any fires there died to embers overnight. Roy can feel the pockets of banked heat ready to burst into flame with the slightest breeze.

He breathes deep and smothers the last dregs of fire. Riza surveys the crater and narrows her eyes.

“_ Sir. _” 

He’s seen it, too. At the end of the crater, the deepest gouge in the earth, there are signs that _ something _ was there. And in the unburnt grass, splashes of dried blood.

They follow the blood trail past a burnt house (not even the ashes are warm, this fire was set long ago) and to a neighbor’s front porch.

Two boys with golden hair are seated on the front porch. One of them has two missing limbs and the brightest eyes Roy has seen on anyone not related to the royal family. The other gazes at him and Riza with an impassively blank expression, despite the tear tracks on his cheeks. They look about ten, and the one in the chair looks so exhausted he’s come back around the other end of manic.

Both have washed off the soot, but not nearly well enough.

Roy steps forward, and two pairs of golden eyes snap to scrutinize his face, his uniform, the flame insignia on his shoulders. He’s expecting the rising heat in the air.

The way the bright-eyed one _ stomps _ his remaining foot and sinks Roy five feet into the suddenly-much-softer ground comes as a surprise. Riza raises her bow, aiming it at the expressionless boy whose hand against his brother’s chair has begun to tremble.

\-----------

Roy is not entirely sure how long that stand-off would have lasted if the boys’ grandmother hadn’t shouted for them to “stop tom-foolin’ and come grab lunch,” but he is extremely glad to be entirely above ground again. The expressionless boy had bent down to whisper something in his brother’s ear before he let Mustang go.

Inside the grandmother’s kitchen, he learns that the crippled boy is named Ed, and the one who rarely blinks as he placidly regards Riza and Roy is Al. He restrains his lingering temper (if you want to piss off a firebender, surround them entirely in Earth or Water) long enough to ask what the _ hell _ kind of bending they were doing to create a fire in their front yard.

Ed stares at them both speculatively, curls his mouth into an unsettlingly feral grin, and explains that that’s just what happens when you leave the Spirit World in a bit of a hurry.

He further explains that his brother had been attacked by a Face-Stealing spirit “last time,” and Ed had gone back to make a deal for his freedom. 

Roy stares at the grandmother at this point because what has she been _ teaching _ these Agni-damned children if they’re traipsing in and out of the spirit world making _ deals _of all things. Everyone knows you don’t make deals with spirits. If you were very, very unlucky, they just might come through.

Her lips thin as she stares back at him with a Look. Years later, Roy will be able to accurately identify this expression as ‘Do not attempt to blame me for this nonsense, they came like that.’

Years later, Roy will use this Look so often he is afraid his face will freeze like that someday.

After hours of a conversation that goes nowhere, with a pounding tension headache, Roy allows Riza to precede him as he leaves the Elrics’ temporary residence. He warns them that the next year, the conscription call will come again. 

It is a not very subtle hint to no longer be here next year.

Ed scowls as they leave, growling as Roy slips in one last remark about his _ short _ temper. Al steps forward with a strange glint in his eye, opens his mouth for the first time since they arrived, and asks, “How do you put out a fire that wants to eat the world?”

His Agni-bright eyes stare straight through Roy’s. He doesn’t appear to be waiting for an answer.

“Very, very carefully,” he answers anyway. Al doesn’t smile, but something in his face eases.

The next year, when they go on conscription call, the Elrics are, thankfully, gone.

Roy barely has time to melt with relief before he gets an urgent messenger-hawk from Falman. Two young earthbenders have shown up at his office and are waiting to see him.

Al is nearly unrecognizable with a bright grin lighting up his face. Ed is somehow standing and walking normally, although his gestures are occasionally stuttered and clumsy. Roy does not have the slightest desire to know.

They tell him anyway.

It’s not easy to hide earthbenders (_ metal _ benders, the Fire Lord would do terrible things to get his hands on one of those) in a Fire Nation military outpost, even if their eyes and the heat they naturally exude both scream ‘firebender.’ It is especially difficult to hide earthbenders like the Elric brothers, who are two different flavors of incredibly terrible and impulsive people. He ends up conscripting them mainly to make sure no one _ else _ ends up as their commanding officer.

When Ed starts actively taking extraction missions throughout the colonies, Roy finally sits him down with a cup of lotus tea and teaches Al how to play pai sho.

**Notes for the Chapter:**

> Mustang: what the fuck did you do that made a CRATER in front of your house  
Ed: *explains*  
Mustang:  
Mustang: sometimes.... questions that are answered.... are w o r s e


	4. The Hope Only of Hollow Men

Hours of flying in the desert sun, a solid thirty-minute climb up a sun-baked tower and down a thin rope, and here they were. Trying to trick a knowledge spirit. Katara wasn’t sure if she should be proud that her brother was attempting to negotiate for knowledge (or, well, a new map, which was close enough) or ashamed that he was so bad at lying that even a  _ spirit _ could tell.

“I-I’m not lying!” he lied, arms waving frantically. “I’m here with the Avatar and he’s the bridge between our worlds. He’ll vouch for me!” Sokka quickly pulled Aang in front of him and gave him a few  _ ‘be-a-good-bud-and-back-me-up-before-I-get-spirit-eaten’ _ pats on the shoulder.

Aang looked unsure but gulped and gamely continued. “Uh, y-yeah! I’ll…”

“Hold up.” Ed strode forward to stand beside Sokka and Aang, staring fiercely into the enormous Owl Spirit’s eyes. “Don’t make promises you can’t keep.”

“Wh-whAt no, no we can keep our promises, we’re TOTALLY good at promising.” Sokka backpedaled slightly at Ed’s glare. “Promises and us are like--”

Ed rolled his eyes and placed a fist against his open palm, bowing deeply to Wan Shi Tong. Katara tried to remember if the irritable Earthbender had ever shown anyone that much respect since he joined them.

She drew a blank.

“We can’t promise not to use anything we learn here in the war effort. We are trying to bring down the  _ Fire Lord.  _ Even if we researched how to knit a freakin’ scarf, we’d probably end up having to assassinate the dick by fresh-knitted scarf or something. We’re kind of desperate here,” Ed stated bluntly.

Al walked forward to join his brother, hands clenched so that she could barely see them tremble. He bowed the same as his brother, precise and practiced.

“What my brother means to say is, we would not intentionally lie to a great Spirit such as yourself. However, as we are currently attempting to stop a war, we cannot promise that any knowledge gained from your library would not influence our actions.” Al straightened, his face placid. “We are unable to be as you are and seek knowledge simply to know it.”

The Spirit hummed consideringly, head swiveling slightly to take in the Earth Kingdom anthropology professor who looked ready to deny their claims, Aang’s wide-eyed silence, the nervous smile on Sokka’s face, and the way Katara’s hands stood ready to uncap her waterskin and attack.

“Since you are here to do as all humans do and steal knowledge merely to wage war…” his voice deepened. “ _ Why should I allow you to leave? _ ”

Ed bristled, but his brother put a hand on his shoulder. “Great Spirit, we understand that you are… weary of humans attempting to use your library to harm others. However, have you considered how much  _ you _ have to lose by letting this war continue?”

Katara blinked. That was. Not at all where she thought Al was going with this. What did the  _ Knowledge Spirit _ have to lose? He was a spirit!

“How many stories and discoveries were lost with the airbenders, and what might their descendants have discovered? How many styles of bending were lost when the Fire Nation rounded up and imprisoned all water benders in the Southern Water tribes? How much knowledge has been lost, burnt, covered over as the Fire Nation controls what is taught within its borders and colonies?” Al’s voice stayed soft and gentle, even while he glanced apologies at Aang, Sokka and Katara. 

Something in his eyes crystallized, diamond-hard as he turned back. “You of all spirits should be intimately aware of what you have to lose if the Avatar and his allies cannot end this war.” The Owl Spirit’s eyes, impossibly, widened.

“wha-BOOM! How do ya like  _ them _ sea prunes?” Sokka cheered. 

In the utter silence that followed, Katara rolled her eyes so hard she almost pulled something.

“Ah… I mean…” Sokka coughed into his fist, standing up straighter. “I  _ respectfully _ agree with my companion, your... Spirit-ly… ness?”

Massaging her forehead, Katara refused to look up. If they all died because Sokka couldn’t keep from ‘wha-BOOM’ing a Great Spirit, she was going to  _ haunt him to death. _

Second death. Whatever.

“We’re looking for an accurate map,” Ed cut in. “And information on how the war started. Once we find it, we’ll leave you in peace.” 

“Is that a deal?” Wan Shi Tong drawled.

“No.” Ed’s voice remained steady. He had angled himself to stand slightly in front of Al, between the Spirit and his brother. “Just a declaration of intent.”

“...Ahhhhh….” The Owl Spirit cocked his head slowly, eyes narrowing like he’d spotted prey. “So it’s the two of  _ you _ …”

Ed’s gloved hands curled slowly into fists. Al’s breathing was so soft and shallow Katara could barely see his chest move.

“You may have two hours,” the Spirit declared. “After that,  _ well… _ ” His curved beak somehow gave the impression of an unfriendly smile.

The brothers bowed, Ed glancing irritably at the rest of the group until they hurriedly bowed too.

“Thank you,” Ed said slowly. “Now. If you could direct us to your collection of maps?”

With a huff, the Spirit took flight, gesturing lazily at a room on the third level above them. Katara was almost sure she could hear him mutter, “Just like his father” as he passed.

Sokka, gaping, followed the Earthbender brothers to the stairs. “How did you _do _that? He was just like, ‘No humans allowed, I’ll kill you dead,’ and then you were like ‘Actually you’re dumb and here’s why’ and he _let us in!_ _How?_ Can _I_ do that?”

Ed rolled his eyes and stomped up the stairs, so Sokka skipped forward to walk next to Al. 

“No, but seriously, can I do that? Can you teach me? Is it even teachable or do you have to--”

Katara sighed and turned to Aang. “Looks like they have the maps covered, do you want to look around while we’re here?”

The younger boy was staring blankly after the brothers, lost in thought. “...oh! Sorry, Katara, I was just…”

“Impressed? Amazed? Awed and astonished that they could talk down a spirit after Sokka nearly got us killed?” Katara asked, grimacing at her brother’s retreating back.

“They’re… they feel different,” Aang said slowly. “Next to the Spirit, I mean. It was weird.”

Katara raised an eyebrow. “Is it the kind of different we need to figure out right now? Or after we finish our two hours in the creepy Spirit library?”

Aang huffed a laugh. “...Nah it can wait.” His eyes brightened with a quicksilver grin. “Come on, Katara! I want to see what they’ve got! Maybe there’s some stuff from the Airbender temples!” Grabbing her wrist, he began to pull towards a staircase on the other end of the hall. 

Katara laughed and ran alongside him, sparing a glance behind her to where Sokka, Al and Ed had nearly reached the third floor. They’d be okay, she thought. It was just a library, really.

And besides, what could happen in just two hours?

**Notes for the Chapter:**

> this chapter was tentatively titled "woe betide anyone who tries to get between the Elric brothers and Knowledge"
> 
> Katara, watching the Brothers team (aka the Elrics plus Sokka) head off into the unknown: I HAVE TOTAL FAITH IN YOU
> 
> Katara, turning to Aang: there's like a 30% chance they all die. Anyway! Let's do some exploring!


End file.
